1. Field of the Invention
The present invention relates generally to semiconductor pressure sensors, and specifically, to a chip-scale packaged pressure sensor.
2. Background Information
FIG. 1 is a schematic cross section of a conventional silicon pressure sensor in a metal can package. As shown in FIG. 1, the pressure sensor package consists of a silicon die 10 having an etched diaphragm 12, a backing wafer 14 usually made of Pyrex, a metal can 16 (e.g., TO-8 or TO-5) which houses the pressure sensor, metal pins 18 for providing external interconnection, and a pressure port 20. The metal can 16 is welded at 22 to maintain a vacuum reference in region 24, or in the case of differential or gage pressure measurements, a top-side pressure port 26 is provided.
FIG. 2 is a schematic cross section of a conventional pressure sensor in a plastic package 28. The plastic package pressure sensor 28 consists of a silicon die 30 having a diaphragm 32, and a backing wafer 34 typically consisting of Pyrex, which is anodically bonded to the silicon die 30, to form a vacuum cavity 36 therebetween for providing absolute pressure measurements. The backing wafer 34 is attached to a bottom portion 46 of the plastic package 28 using an epoxy or RTV die attach. A gel overcoat 38 (e.g., silicon gel) is provided over the silicon die 30 for communicating pressure from external gaseous media. The plastic package 28 further includes a lid 40 having an opening 42 for directing external pressure to the sensor. The silicon gel provides a minimal amount of protection from adverse effects of the gaseous media for the sensor, circuits and wire interconnects.
In one embodiment, the present invention comprises a chip-scale sensor package. The chip-scale sensor package includes a semiconductor substrate having a sensor region, and a semiconductor cap having a recess. The semiconductor cap is bonded to the semiconductor substrate with a thermocompression bond to form a cavity therebetween. The semiconductor substrate and/or the semiconductor cap may optionally include one or more semiconductor devices such as an electronically trimmable integrated circuit fabricated thereon using conventional integrated circuit fabrication techniques. In addition, the semiconductor substrate may optionally include an integral stress isolation flexible region for isolation of the sensor region.